Minisplit or window units for 10 rooms?
I have a rental house in Climate Zone 2 with 9 bedrooms, meaning about 11 total rooms that need to be cooled/heated. Right now that means window AC’s and electric space heaters, the latter of which is a no-go for getting property insurance. So I’m gonna install either a ductless mini-split or combo heat/cool window units, and I’m weighing the pros/cons.
If I go with window units, I’d use one of the new-fangled heat/cool combos that use a heat pump for heating, like Frigidaire FFRH0822R1. They don’t heat when it gets very low (can’t find the spec right now, but I think I saw around 45°F), but it usually doesn’t get that cold here, and when it does, the insurance company will allow electric space heaters as *supplementary* heat, as long as the thermostatically-controlled window unit is primary.
Also, if I go with window units, I might cut holes in the walls to install them so I can seal them well, and not waste the windows.
I’ve read various articles on pros/cons of mini-splits and window units. One idea is that mini-splits are usually oversized when the rooms are small (and mine are, generally 100-150sf), but I’m skeptical that would be a big performance penalty vs. window units. If they don’t run long enough to remove humidity, dehumidifiers seem like an option.
WINDOW UNITS: Much cheaper (even if I cut holes in the walls), can self-install, can easily swap out a unit when one fails, won’t require dehumidifiers.
MINI SPLIT: More efficient (?), easier to seal, less heat conduction through walls, quieter.
Comments?
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Do a load calculation (I've used coolcalc.com happily). But I think you'll find the minisplits much more expensive and likely quite oversized. Can't imagine that you'd want to pay the additional cost of dehumidifiers as well. So if tenants will tolerate the noise of window units through the wall, that seems the way to go.
Is this a boarding house?
Is there any room for ductwork? A slimduct approach would give the best efficiency.
If you are going for the cheapest option, then install enough electric baseboard or small fan forced electric units to cover heating. Use decent window units for cooling and maybe heating down to as low as they operate.
The obvious low cost to install choice missing from your list is the Package thermal Air Conditioner or PTAC found in most hotel rooms. They can be had with resistance heating or heatpump as needed. They fit in a hole in the wall called a sleeve. Be sure to pick one that uses a common sleeve size to make finding a replacement easy when the time comes.
https://www.amazon.com/Amana-PTAC-3-5kW-Heater-PTH153G35AXXX/dp/B07GGDMFMP
I doubt you need a unit in every room but the insurance may require heat in each room consider the electric base board heater to keep them happy.
If you are paying the electric bill get the minis.
Walta
>"If you are paying the electric bill get the minis."
It takes a LONG time to pay off the up-front difference in cost between a PTHP and a ductless mini-split, even in high electricity price areas.
If you're installing ELEVEN of them you might be able to get a good deal on an HVAC contractor dozen 3/4 ton 115VAC Midea or Gree, which have about the same online price as a half ton PTHP. Most of those have more than adequate heating capacity for any 150' bedroom, and enough cooling capacity for a west facing bedroom with single pane windows. But it'll still have a higher installed price than a DIY PTHP solution.
Thank you all for the replies. I'm leaning towards heat-pump window units at this point.
The house isn't a boarding house, though I don't see why that matters.
Ductwork is incredibly expensive, and for no advantage that I can see.
I couldn't find any advantage of PTAC over a heat-pump window unit, and the PTACs come with some downsides--much higher cost, much harder to install, and I couldn't find a 120V model that supplies as much heat as a heat-pump window unit.
I'm not paying any utilities. That's a recipe for waste. When I lived in a Las Vegas apartment where utilities were included, another tenant bragged to me about he left the AC on 68°F 24/7.
Do the electrical panels that serve each unit have room to add a dedicated 20 or 30 amp 240 volt circuit for heating and cooling? I am guessing not The last thing you want is to plug in a window unit into an already overloaded circuit.
This insurance inspector or the next could easily decide window units are not permanently installed and do not qualify as central heating leaving you uninsurable again.
The way I see it sooner or later every property gets sold and window units lower the property’s value. Spending money to lower your property value seems like a poor choice.
I am not suggesting you paying the heating and cooling is a good idea. Just asking as it does happen sometimes and investing in high efficiency equipment could make sense.
Walta
>>The last thing you want is to plug in a window unit into an already overloaded circuit.
Like I said, the tenants are *already* using window units and electric space heaters. Heat-pump window ACs use *less* energy to heat than electric space heaters, so going with those would lower the electrical load.
>>This insurance inspector or the next could easily decide window units are not permanently installed...
Like I said, the insurance company agreed that the window units are acceptable.
>>The way I see it sooner or later every property gets sold and window units lower the property’s value. Spending money to lower your property value seems like a poor choice.
Like I said, the tenants are *already* using window units and electric space heaters. Replacing the existing window units with combo cool/heat units certainly wouldn't lower the property's value.
So what did you do? I did a Mr Cool DIY 12k/120v at my house and am very pleased. I'd probably go a different route now.
You didn't mention budget or what the avg rent was. Another way to look at it, is if it prevents you apt from being empty even one month it is probably worth it.
I just found some units from a company called Innova out of Italy, that are full self contained for about $3,000. That is no outdoor unit. they are heat pumps and you will need a path for condensate.
I went with the Frigidaire FFRH0822R1 combo AC/heat heat pump units. My primary motivator in going with these over resistance was that I didn't think I'd need to upgrade the electrical service panel or run new circuits like I'd have to do to support 1500W resistance panels, as the heat pump was supposed to use only 775W. After I got the combo units I realized that there's a backup resistance heater that uses 1290W, almost as much as resistance panels. The backup resistance panel can't be turned on or off manually, the unit decides when to run it, and I don't yet know what its criteria is. (I'll call Frigidaire when I get a chance, but I don't expect them to provide an answer.) In the meantime, after making a breaker map, I saw that I had to run only one new circuit to get each unit on a separate circuit, and I don't think we'll overload the panel because the backup resistance heat probably won't run in most of the units at the same time. We haven't tripped any breakers yet.
Are they quiet? or more likely quiet enough? The Mr Cool, uses about 1/3 less power and is far more effective.
They're window units. You know how loud window units are. I didn't notice them being appreciably louder or quieter than other window units.
They were significantly cheaper than Mr. Cool ($483 vs. $3000), and considering I bought 12 of them, no way would I have spent an extra ($3000-483)x 12 = $30,204 for no commensurate benefit.